Pneumatic system of and apparatus for handling railway-switches



'- 4 Sheets-Sheet 1. I J. W. THOMAS, Jr. PNEUMATIC SYSTEM 0]? ANDAPPARATUS FOR HANDLING RAILWAY SWITCHES.

No. 520,812. Patented June 5, 1894.

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4 Sheets-Sheet 2.

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J. W. THOMA$,JT. PNEUMATIC SYSTEM OF AND APPARATUS FOR HANDLING RAILWAYSWITCHES.

No. 520,812. Patented June 5, 18%

%aoem (No Model.) 4 Sheets-Sheet 3.

J. W. THOMAS, Jr.

PNEUMATIC SYSTEM OF AND APPARATUS FOR HANDLING RAILWAY:

SWITCHES:

No. 520,812. Patented June 5. 1894.

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- J. W. THOMAS, Jr. PNEUMATIC SYSTEM OF AND APPARATUS FOR HANDLINGRAILWAY SWITGHHS. No. 520,812. Patented June'5, 1894.

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My invention is directed mainly to the hand- Nrre STATES ATENT Fries.

JOHN W. THOMAS, JR, OF NASHVILLE, TENNESSEE.

PNEUMATIC SYSTEM OF AND APPARATUS FOR HANDLING RAILWAY-SWITCHES.

, SPECIFICATION forming part of Letters Patent No. 520,812, dated June5, 1894.

' Application fileclIebruary 24,1894. 7 Serial No. 501,399. (No model.)

To all whom it may concern Be it known that I, JOHN W. THOMAS, J r., ofNashville, in the State of Tennessee, have invented a certain new anduseful Pneumatic System of and Apparatus for Handling Railway-Switches,of which the following is a ling of railway switches; but in some of itsfeatures it is applicable to the handling of railway signals as well.

The main and controlling feature of my invention is the manipulation ofthe valve or valves admitting air to and exhausting it from the workingcylinder of a railway switch by means of two pneumatic pistons (ofeither the differential or the equalizing type as hereinafter described)each actuated independently of the other by means of separate anddistinct controlling pipes both of which contain air at more thanatmospheric pressure at all timesthe pistons being subjected, on thesides opposite those on which the controlling pipes are located, to airpressure opposing that in the controlling pipe, and being actuated andcontrolled in their movements by alternately and at proper timesreducing the pressure in the controlling pipes below, and restoring itto, the maximum. v

The object which I have in view, and which is attained by the foregoingmethod of handling the valve or valves, is to. insure speed, andcertainty in the operation of the parts, as well as immunity fromaccident.

The invention resides also in the pneumatic appliances constituting whatI term the indicator mechanism, employed by me to indicate to theoperator in the tower whether the'switch has responded properly to themovement of the switch operating lever, and to restrain that lever frommotion to an extent sufficient to unlock the signal mechanism untilafter the switch has properly responded; it also resides in a valvemechanism controlled by the movement of the switch, for changing thecurrents-of air by which the indicator mechanismis operated; and itfurther resides in other detailswhich will be developed in the course ofthe following specification.

To enable others skilled in the art to understand and use my inventon Iwill now proceed to describe more particularly and in detail the mannerin whichthe same is or may be carried into effect, by reference to thedrawings accompanyingand forming part of this specification. g i

In the accompanying drawings-Figure 1 is an axial section of theworking, or switchactuating, cylinder and the valve mechanism forcontrolling the supply of compressed air to said cylinder. Fig.2 is asectional side elevation of the operating lever (located in the tower)and the parts connected therewith through the agency of which themovement of theswitch is controlled. Fig. 3 is a vertical sectionenlarged of the mechanism through which the operating lever is caused tointermittently engage the controlling valve. Fig. 4c is a face elevationof the spring device which engages the stem of said valve. Fig. 5 is aplan (with the working cylinder in section), and Fig. 6 is alongitudinal vertical section of the valve mechanism operated by themovement of the piston rod of the working cylinder.

Figs. 7, 8, 9, and 10, are views respectively in plan and side elevationof that end of the tappet of the operating lever which engages theindicator or, locking pin-showing the same in the different positionsthey assume during the operation of throwing the switch. Figs. 11 and12, are axial sections of modified forms of the valve mechanism for theworking cylinder. Fig. 13 is a like section of a modified arrangement ofthe indicator cylinder andparts connected therewith.

1 is theworking cylinder; 2 is its piston (suitably packed); and 3 isthe piston rod through the agency of which the switch is operated. Themeans employed for this purpose may vary; one known arrangement ofmechanism is shown in plan in Fig. 5, comprising the reciprocatory bar 5pinned to the outer end of the piston rod and provided with a pin awhich engages and works the crocodile jaw lever a pinned to somesuitable base, and connected to the switch points a by a suitableconnection a The same bar 5 through suitable intermediary a alsov worksthe switch look. I attempt no detailed description and illustration ofthese parts however, inasmuch as they form no part of my invention andare well known to those skilled in the art.

The working cylinder is provided with ports 11,11, one at each end,which by suitable passages or pipes communicate with like ports in thevalve chest 16. This chest is also provided with two exhaust ports 12,12, and with a supply pipe 13 through which air from the main compressedair supply enters the chest. The ports 11,12 are controlled by a D slidevalve 8, which is actuated by a differential piston 5, 5', the slidevalve being held between collars on the stem of the differential piston;the ports 11', 12', are controlled by a like slide valve 8', which inlike manner is connected to and actuated by a differential piston 6, 6'.In one head of the valve chest is an inlet 14 and in the other andopposite head of the chest is an inlet 15. Inlet 14 by a pipecommunicates with a like numbered port 14 in the chest 38, controlled bya slide valve 36, (Fig. 2,) connected to the switch operating lever 32in the tower. Inlet 15 by an independent pipe communicates with the likenumbered port 15 of the valve chest 38 in Fig. 2. In chest 38 is anexhaust port 49 between the ports 14 and 15. This port 49 is designed tobe closed by a relief or pop valve set so as to blow off at any desiredpredetermined pressure-say above fifty pounds to the square inch, if thenormal pressure in the controlling pipes and valve chest is, as I preferit should be, sixty pounds to the square inch. Compressed air from themain supply enters the chest 38 through a pipe 39 controlled by areducing valve 40. In the system I have adopted, while I work with sixtypounds pressure in the controlling pipes 14, 15, yet for certain reasonshereinafter explained I prefer that the main supply from which this airis drawn shall be at eighty pounds pressure to the square inch, and Itherefore employ the reducing valve 40 to .bring down the pressure tosixty pounds.

In the position of parts shown in Figs. 1 and 2, the controlling valve36 is so located as to bridge the ports 49, 14, and to uncover the port15. Thus air at sixty pounds pressure enters through inlet 15 of valvechest 16 (Fig. l)and acting against the larger head of the differentialpiston 6, 6', overcomes the counter pressure of say eighty poundsexerted upon the smallerhead of the piston, and

forces it to the left bringing its slide valve 8 in position to bridgethe ports 11, 12', and consequently opening the exhaust to the righthand end of the working cylinder. At the same time pressure upon thelarger head of the other differential piston 5, 5', is rednced to sayfifty pounds by reason of the inlet 14 at that end of the valve chest 16being in communication with the exhaust or relief port 49 (Fig. 2), andconsequently the superior pressure upon the smaller head of thedifferential piston 5, 5', forces it to the left, thus uncovering theport 11, and permitting compressed air at full pressure (eighty pounds)to enter the left hand end of the working cylinder, with the effect offorcing the piston 2 to the right. To reverse, the

controlling valve 36 is shifted to bridge ports 49, 15, and uncover port14. The effect is to reduce pressure to fifty pounds at inlet 15 and toincrease it to sixty pounds at inlet 14 with the result of shifting thedifferential pistons in Fig. 1,so that the valve 6, 6,willnow (by theslide valve 8') admit compressed air to the right hand end of theworking cylinder through uncovered port 11, while valve 5, 5', (by theslide valve 8) will bridge ports 11, 12, thus opening the left hand endof the cylinder 1 to the exhaust, and consequently causing the piston 2to move to the left. Under this arrangement it will be noted that thevalves which admit air to and exhaust it from the working cylinder aresubjected to maintained compressed air pressure from both sides, and areoperated by means of two controlling pipes-one for each valve-by thealternate increase and diminution of pressure in which the valves areshifted-both of these pipes containing at all times air at more thanatmospheric pressure.

My reason for having a high air pressure say eighty pounds-in the mainsupply pipe, and reducing it toamaximum of sixty pounds in thecontrolling pipes 14, 15, is that practice has demonstrated that afterthe partial exhaust to fifty pounds pressure in the same pipe will berestored to sixty pounds more rapidly, than if the pressure in the mainsupply pipe were no greater than the maximum pressure in the controllingpipes, and therefore the valves for admitting and exhausting air fromthe working cylinder will be shifted more quickly.

In the practical working of this system under the conditions aboveindicated, fractures in the pipe line of the controlling pipes 14, 15,may occur, as for example in the pipe 15, in Fig. 1, which for the timebeing happens to be the high pressure pipe. The consequent leakage mightresult in such a reduction of pressure in that pipe as to cause the nowsuperior eighty pounds pressure within the chest 16 to force valve 6, 6,to the right. To guard against movement of either one of thedifferential pistons from this cause I prolong their stems 7, 7', intotappets 9, 9' which extend on opposite edges of a transversely slidingdog 10, adapted to enter a notch in one or the other of the tappets andthus to lock it (and consequently its valve) against movement. Thetappet 9 is thus locked in Fig. l, and cannot be unlocked until theother piston 5, 5', and consequently the tappet 9, first move to theright far enough to bring the notch in that tappet opposite the dogwhichmovement of course cannot take place until pressure is restored tonormal in the controlling pipe 14 of the differential piston 5, 5'.Again it may happen that pressure in the interior of the chest 16delivered through main supply 13 will chance to fall so much beloweighty pounds as not to be able to resist the pressure in pipe 14,although that pressure, under the conditions supposed in Fig. 1, hasbeen reduced to fifty pounds. In this event the valve 5, 5', would, bythe superior pressure exerted through pipe 14, be forced to the right,thus opening the right hand end of the working cylinder to the exhaustand at the -same time unlocking the tappet 9' of the other valve 6, 6'.It under these conditions the pressure in pipe 15 should by any chancefall so as not to-be able to resist the internal pressure in the valvechest, the differential valve 6, 6, would move to the right, thusopeningthe air supply to the right hand end of the working cylinder,with the result of shifting the switch. In order to guard against anysuch contingency I provide for each piston valve a retaining pin 21,attached to a piston 18 in a cylinder 17 set in the valve chest 16 withits inner end communicating with the interior of said chest. The piston18 is inwardly pressed by .a spring 19, the stress of which is regulatedinterior of the chest is normal, it will suffice to push up the piston18 against the force-of its spring far enough to carry the pin 21 out ofthe path of the collar or flange 22, or 22, on the stem of thedifferential valve 5, 5', or 6, 6'. As soon however as pressure fallsbelow normal the pin 21 drops behind the collar, in position to preventany inward movement of that valve (in this instance valve 5, 5,) whichis for the time being the low pressure or exhaust valve, and the tappet9 of which looks the dog 10 into engagement with the other tappet 9.There should be in each of the adjusting nuts 20 an aperture to permitthe escape to the atmosphere of any air which may happen to leak throughbetween the pistonlS and its .cylinder.

The valve 36 (Fig. 2) is operated, as before said by the operating lever32. This lever is provided with a suitable latch 33, to engage astationary notched quadrant by which it can be held in any one of thethree positions A, B, O; and it is connected as customary to the tappet31 of an interlocking apparatus by which all levers for operatingsignals which give the right of way to a train over the switch, arelocked until the switch is fully thrown. For this reason the connectionbetween the operating lever 32 and its valve 36 must be such that thevalve will be moved its entire throw during the first half of themovement of the lever 32 in either direction, and remain stationaryduring the remainder of the stroke, thus permitting the lever sufficientmovement, after the valve is thrown, to shift the interlocking tappetfar enough to unlock the signal levers controlled by it; and for thesame reason there must be combined with. the interlocking tappet meanswhereby its movement to this extent is prevented until it is certainthat the switch has been fully thrown or shifted. The means lastreferred to will be presently described.

I will now describe the mechanism by which end of the stem 37 of valve36.

the operating lever after throwing. its valve permitted further movementWhile the valve remains at rest. Various mechanical devices maybeemployed for the purpose. The mechanism shown in the drawings (Figs. 2,3, and 4) is that which I now prefer.

The tappet 31 is supported by and slides in suitable guides on the table50. The shorter arm of the operating lever is pinned to the end of aconnecting rod 34, which passes through guideways (in which it can slideor move lengthwise) in a frame or casting 35, bolted to the side of thetable 50. In this same frame or casting is a guideway for the In thisstem are two notches 44, 45, and connection is established between rod34, and the stem 37,

by a dog 43, carried by the rod, which enters one or the other of thenotches in the valve stem. So long as the parts are thus connected, thestem and rod will move together as one. But manifestly in order to admitof the independent further movement of the operating lever after thevalve has been thrown, the connection between the rod 34 and the valvestem must be, not permanent, but temporary and intermittent. To this endI attach the dog 43, to the end of a bowed spring arm 42, fixed at itsother end to the rod 34. This arm is provided at the end which carriesthe dog, with laterally projecting bosses 48, which run upon doubleinclines 47, 46,the apex or highest point of the incline being midway ofits length-which length is equal to the traverse of the rod 34occasioned by the full stroke of operating lever 32. And the distancebetween the notches in the valve stem is equal to one half of thisdistanceas indicated in Fig. 3.

In the position of parts shown in the drawings the dog 43 is engagedwith the notch 44, and the operating lever is at one extreme of itsmovement, in its A position. In throwing it over to its 0 position theoperation is as follows: This movement of the lever through theconnecting rod 34 also moves the valve 36. As the bosses 48 move overthe incline 46, the dog 43 is gradually withdrawn from the notch 44 and,as the apex or highest point of the incline is reached, finally quitsand is disengaged from the notch-thus releasing the valve 36 from thecontrol of the lever. By this time however, the valve has been fullythrown. All this is accomplished by the time the operating lever reachesits B position, thus leaving the remainder of the movement from B to Uto effect the full movement of the interlocking tappet 31. By the timethe operating lever reaches its 0 position, the dog 43, hastraveled'down the other incline 47, and has reached and engaged theother notch 45 in the valve stem,Whicl1 notch by the previous movementof that stem was brought to position to meet the dog 43 at this time.Thus on reaching its 0 position the operating lever is once more inconnection with the valve. In throwing the lever back IZC from C to Aposition, the same sequence of operations takes place. By the time thelever reaches B, the valve will have been thrown, and the dog 13 willhave been disengaged from the notch 45, thus leaving thelcver free tomove from B to A without further influencing the valve. On returning toA position, the parts reassume the position indicated in Fig. 2.

I now pass to a description of the instrumentalities by which theoperating lever in being thrown from one extreme of its movement to theother is prevented from passing beyond its B or middle position untilthe switch has been fully thrown. These instrumentalities areillustrated in Figs. 2, and 5 to inclusive. The tappet 31, as seen inplan view in Figs. 7 to 10, has in it two longitudinal slots or recesses30, 'one in each edge. In conjunction with these slots are provided theindicator pins 29, 29'pin 29 working in conjunction withslot 30, andpin29' working in conjunction with slot 30. These pins are so arranged thatwhen the one is up, the other-is down,and they are actuated thus to moveby pneumatic appliances controlled by or from the switch in the mannerhereinafter described. It will be suiiicient for the present to saythat, as shown in Fig. 2, each pin is connected by an oblong rectangularframe 28, or 28' (shown detached in elevation on the left of Fig. 2) tothe stem 26, or 26' of a piston 25, or 25',adapted to move up and downin a cylinder 23, or 23', and upwardly pressed by a spring 27, or 27, orweight or any other suitable instrumentality for the purpose, so as toproject the pin into its appropriate slot in the tappet. Compressedairdelivered into the cylinder through an inlet 24, or 24, will atproper times by its superior pressuredepress the piston and so lower thepin out of engagement with the tappet. The two cylinders 23,23 aresecured to the table, and each frame 28 or 28', straddles and moves inguides on the exterior of its cylinder.

The parts are shown in normal position in Figs. 2 and 7. The pin 29 isdown and under the solid portion of the tappet. The pin 29' is up and inthe end of its slot 30 nearest to the operating lever.

To shift the lever from its A to its 0 position, the lever first movesfrom A to B-the length of the slot 30' permitting this limitedmovement-at the end of which the pin 29 will be at the far end of theslot 30, and the pin 29 will be opposite to or just under the near endof its slot 30. This movement of the lever from A to B should suifice asalready explained to throw over the switch. If the switch is not fullythrown over, the pins will remain in stat'u. quo, and further movementof the lever toward its C position will be prevented by the lockingactionof the pin 29'. But if the switch is fully thrown over, then, bythe action of valve shifting mechanism to be presently described,compressed air will be exhausted from over piston 25 of cylinder 23through port 24, and

will be supplied to cylinder 23' through port 24', and consequently thepin 29' will drop and the pin 29 will rise as indicated in Fig. 8. Withthe parts in this position the operating lever is free to be moved toC--the tappet, when the lever reaches this .point, occupying theposition shown in Fig. 9. In returning the lever from C to A, itsmovement from C to B will bring the parts to the position shown in Fig.l0--provided of course the switch has been fully thrown; and furthermovement of the lever from B to A will be permitted-the parts, when thelever again reachesApositionappearingasinFigs.2and7. This result isreached, as already indicated, by alternately and at proper intervalsdecreasing and increasing the air pressure over the pistons 25 and 25'.The manner in which I attain the result is as follows-referring moreparticularly to Figs. 5 and 6: The rod 5, which is pinned to the pistonrod 3 of the main cylinder 1 (Figs. 1 and 5) has more throw than isneeded to handle the switch. In other words the rcciprocatory rod 5moves farther in each direction than is required for handling theswitch. This excess of. movement I avail of to operate the valvemechanism by which the supply of compressed air to the indicatorcylinders is controlled-the arrangement being such that the operationcannot take place until after the switch has been fully thrown. Thearrangement of mechanism for this purpose is as follows: Immediatelyabove the rod 5, and fixed in a stationary position so that the rod canslide beneath it, is the valve chest 51, supplied with slide valves 52,53, which either can be cast in one piece, or can be made separate asshown, in which latter event they will be held between collars orflanges on a piston rod 54:, ends of which project out from oppositeends of the chest through suitable stuliin g boxes. I remark at thispoint that to the right of valve 53 there is represented still anothervalve which has no designating numeral. This particular valve togetherwith the passages (unmarked) controlled by it, are placed in the chest51 for convenience, but have no close relation to the present invention,being merely instrumentalities in the nature of what may be termed apneumatic selector, for operating the pneumatic pistons of two signals,one or the other of which will be operated according to the position ofthe switch; they form part of another application for Letters Patent inmy name of even date herewith, for an improved pneumatic signal systemand apparatus, and requires no description here.

The valve 52, operates in connection with ports 57, 58, 59-57communicating with the main compressed air supply; 58 (through asuitable pipe) with the opening 2 1 in cylinder 23' over piston 25'(Fig. 2); and 59 with an exhaust controlled by a properly set pop orrelief valve. The valve 53 operates in connection with similarlyarranged ports 60, 61,

- 62, of which 60 communicates with an exhaust controlled by a properlyset pop or relief valve; 61 (through a suitable pipe) with the open ng24 in cylinder 23 over piston 25; and 62 with the main compressed airsupply. In practlce one pop orrelief valve will serve both ports 59and.60. The arrangement is such that when theone valve is in position toputthe main supply in communication with ts indicator cylinder, theother valve will be in posltlon to open the other indicator cylinder tothe exhaust. From one of the main supply portsin this instance port57there leads a permanently open by-pass 55 to the interior of the valvechest 5l'the latter thus being constantly supplied with compressed air,for the purpose of balancing the valves.

The shifting of the valves is effected by means of two knockers 56,carried by the rod 5, and located one beyond each end of the valve stem54.

The position of parts represented in Fig. 6 1s that occupied by themwhen the switch is normal, and the lever 32 in the tower is in theposition shown in Fig. 2. Valve 52 is in position to put its exhaustport 58 in communication through port 59 with indicator cylinder 23',thus permitting the indicator pin 29' to rise, while valve 53 is inposition to put its compressed air supply port 62 in communicationthrough port 61 with indicator cylinder 23, thus causing the indicatorpin 29 to drop.

It will be borne in mind that, as hereinbefore stated, the rod 5 hasmore movement than is needed to throw the switch.

In reversing or throwing over the switch the operation of the parts inquestion is as follows: By'movement of the operating lever 32 from itsAto its B position,air is admitted to the switch operating cylinder in adirectlon to cause the rod 5 to move to the left. The knocker 56 on theright hand end of the rod is such distance away from the valve stem 54:,that the rod 5 can certainly move at least the full distance required tothrow the switch before the right hand knocker meets the end of thevalve stem. Indeed I prefer that this red 5 should move considerablyfarther than is needed to throw the switch before either knocker meetsand shifts the valve stem-the shifting of the valve stem taking placesay only during the last half inch of the movement of the rod 5. Atanyrate it is only after the switch has been fully reversed andlocked,thattherighthandknocker 56, meets the valve stem 54:,and theremainder of the movement of the rod is just sufficient to cause theknocker to shift the valves 52, 53, the former now supplying compressedair to its cylinder 23', and the latter partly exhausting the air fromits cylinder, thus causing the indicator pin 29 to rise, and the pin 29'to descend, to the position represented in Fig. 8. In this way, it willbe seen that the indicator pins 29, 29 are so controlled by thepneumatic mechanism, the operation of which is directly dependent uponthat of the switch throwing devices, that the switch operating lever 32in moving from A to O or vice versa, cannot get beyond its B positionuntil after the switch has been fully thrown and set.

The operation of the system as a whole has been sufficiently indicatedin the course. of the foregoing specification, and needs no furtherdescription.

It will be noted that in this system the manipulation of the valveadmitting air to and exhausting it from the working cylinder of theswitch is controlled by two controlling pipes-one for each valve or setof valves bothof which contain air at more than atmospheric pressure atall times, these pressures being variable within limitsthat in the onerising, as that in the other is reducedand acting to oppose more or lessthe air pressure exerted in the contrary direction upon their respectivevalves. These conditions I believe to be essential to the practicaloperation of the system, and involves much more than a mere duplicationof the controlling devices.

At first sight it might be imagined that, for example, one half of thevalve operating mechanism and one of the controlling pipes in Fig. 1might be dispensed with, and the admission of air to and its exhaustfrom'the cylinder might be controlled by a single valve (8 for instance)through its two ports 12, 11, and a third port answering to 11' placedon the side of 12 opposite to that on which port 11 stands. But in anysuch arrangement with one controlling pipe only the switch is veryliable to fly over. If for example the controlling pipe should burstwhile maximum pressure was on it,'the switch would at once fly over. Soalso would it, if the controlling pipe were at minimum pressure and themain supply pipe leading to the valve chest should spring a leaksufficient to reduce the pressure in the chest below that in thecontrolling pipe. Of course the latter contingency might be avoided ifthe valves were worked at such low pressures as that minimum pressurewould be 0. But it is very necessary to work at high pressure in orderto handle switches with the requisite rapidity. If for example maximumpressure were ten pounds and minimum 0, itwould take about twice as longto operate the switch for the reason that at these low pressures airwill flow more slowly than it will at high pressures. rience hasdemonstrated that no switch or signal system in which all the air in thecontrolling pipe is exhausted at any stage of the operation can be madeto work successfully as to speed. To the attainment of speed, maintainedhigh pressure, with as little variation as practicable between themaximum and minimum pressures, is requisite; and no such systeminvolving, as has heretofore been the case so far as I'know, the use ofone controlling pipe only, can be made really secure against the switchflying over, for the one IIO In fact expemove or the other of the switchmust be directly dependent upon reduction of pressure in the controllingpipe, and it does not matter whether the reduction be occasioneddesignedly or by accident-the result will be the same.

lVorkin g at the pressures which, as hereinbefore indicated I prefer towork at, it requires a reduction of ten pounds pressure in thecontrolling pipes 1 1, 15 in order to properly handle the switch bymeans of the mechanism shown in Fig. 1. By eliminating however the slidevalves S, S, and to this extent reducing friction, I have found I canhandle the switch with a seven pound reduction of pressure.

A plan by which the valves 8, S, can be dispensed with is illustrated inFig. 11. The smaller pistons 5' and 6 of the diiferential pistons arethemselves used to control the ports by which air is exhausted from andadmitted to the working cylinder; and the exhaust opening or openings 12in each case (corresponding in function to the ports 12, 12' in Fig. 1)are located in that part of the valve chest which is embraced betweenthe larger and smaller pistons or heads of each differential piston. Inother respects the arrange ment does not differ from that shown inFig. 1. So too I can, and have, dispensed with differential pistons,using in lieu thereof equalizing pistons-that is to say pistons each ofwhich has in it, or in that portion of the valve chest which ittraverses, a port through which air can gradually pass from one side ofthe piston to the other in order to finally equalize the pressure onboth sides after it has been reduced from, or restored to, the maximumon the sideof thecontrolling pipe. An arrangement for this puropse isrepresented in Fig. 12. In this arrangement the equalizing pistons areshown at 63, 63'. Each is contained in a chest or compartment 71, 71,distinct from and non-communicating with the other; and each has a valvestem 61 or 64', connected to a slide valve 65 or 65'. Valve 65 controlsports 11, 12, similar to those in Fig. 1, and also (unlike thearrangement shown in Fig. 1) a port that communicates with the maincompressed air supply. Valve 65 e011- trols similar ports 11', 12, 70.In the outer head of the one valve chest 71 is the controlling pipe 15,and in the like head of the other chest 71' is the controlling pipe 14.In each piston is an equalizing port 66, or 66, through which air cangradually pass from one side to the other of the piston according to thepreponderance of pressure so as to finally equalize the pressure on bothsides of the piston. The air capacity of the chests is preferablyincreased by reservoirs 67, 67' one for each chest.

\Vith the parts in the position represented in Figs. 12 and 2respectively, then, if they were operating together, the controllingpipes 14 and 15, of Fig. 12, would lead to the like designated ports inFig. 2.

This would be the position of parts when the switch was normal-pipe 15,chest 71, and reservoir 67 containing air at say sixty pounds pressure,and pipe 14:, chest 71 and reservoir 67' containing air at say fiftypounds pressure. The air from the main supply for the working cylinderthrough ports 70, 70, will be at eighty pounds pressure. To reverse theswitch, pressure is reduced in the pipe 15, and as this reduction takesplace faster than air can pass through the equalizing port 66 from thereservoir 67, the piston 63 will be forced to the left by the superiorpressure on its reservoir side thus closing the supply and opening theexhaust to the left hand end of the working cylinder. At the same timepressure in pipe 14 is restored to maximum more quickly than air canfeed through the equalizing port 66 of piston 63, and consequently thatpiston will also be forced to the left, thereby closing the exhaust andopening the supply to the right hand end of the working cylinder. Thepressure in the chest 71 now begins to equalize until it is reducedtofifty pounds on each side of the piston 63, like equalization takesplace in the chest 71', until the pressure-there upon each side of thepiston is sixty pounds.

In some instances, as for example when the switches are a considerabledistance from the tower containing the switch operating lever and theindicator pins, the equalizing arrangement just described can be used togreat advantage in connection with the indicator cylinder for thepurpose of hastening the action of the indicator and thus rendering itpracticable to handle the parts more quickly.

Fig. 13 represents one of the indicator cylinders and an equalizingpiston and chest thus combined-the cylinder is supposed to be theindicator cylinder 23 of Fig. 2, and the equalizing piston, a pistonsimilar to 63 of Fig. 12. Similar reference numerals in these figuresrepresent corresponding parts. Fig. 13 therefore needs no detailedexplanation further than to say that the inlet 2a of the indicatorcylinder 23, communicates with the supply port of the equalizing chest,and the head of that chest with the port 61 of the valve chest in Fig.6. In this way I am enabled for the purpose of operating the indicatorto take compressed air from the main supply at a point in closeproximity to the indicator. This arrangement permits of all the airbeing exhausted out of the indicator cylinders, thus allowingthe springor its equivalents to force up the locking pin more quickly.

While the differential piston and the equalizing piston hereinbeforedescribed are specifically diiferent types of pneumatic piston, yet forthe purposes of my invention and in the connection in which Iuse themthey are the equivalents one of the other.

I have represented the indicator pistons as influenced on the reverseside by a spring, but in lieu of spring pressure, I can use airpressure, whether constant or intermittent, or a weight or otherappliance.

I remark in conclusion that I am aware that it is not new in a generalsense to take the air for the working cylinder from the main supply at apoint in proximity to the cylinder, through the agency of pneumaticallyoperated valve mechanism, controlled from a distance through the agencyof air by some mechanically operated lever or like appliance; nor is itbroadly new to admit air to and exhaust it from the working cylinder bymeans of a differential piston valve mechanism. Both of these featuresbroadly considered I understand to be-old and public property. I desirefurther to remark that in my equalizing piston arrangement, thecompressed air for the working cylinder is taken from the main supply ata point in proximity to the cylinder, and that the main supply is indirect communication with the working cylinder by way of the D slidevalve controlled by the pistonno part of the air from the controllingpipe being used in the working cylinder.

The use of an equalizing piston mechanism on the indicator cylinder, asillustrated in Fig. 13, is applicable whether that indicator be used inconnection with a switch lever, as

herein described, or a signal lever as in my companion application ofeven date herewith for pneumatic system of an apparatus for handlingrailway signals.

What I believe to be new herein and of my own invention is as follows:

1. The method of manipulating or working the valve or valves admittingair to and eX- hausting it from the working cylinder, which consists insubjecting each of two pneumatic pistons to the action of a columnofcompressed air separate and distinct from that which acts on theother, and delivered through controlling pipes, one for eachpiston,containing air at more than atmospheric pressure at all times, thepistons being subjected, on the sides opposite those on which thecontrolling pipes are located, to air pressure opposing that in thecontrolling pipes, and being actuated and controlled in their movementsby alternately and at the proper times reducing and restoring thepressure in the controlling pipes, substantially as hereinbefore setforth.

2. The combination of the two pneumatic pistons, the controlling pipesone for each piston, the operating lever, the valve actuated thereby andconnections substantially as described between said controlling pipesand the ports controlled by said valve, whereby the one controlling pipeis placed in communication with the. exhaust when the other is incommunication with the source of compressed airsupply, substantially asand for the purposes'hereinbefore set forth.

3. The combination with the operating lever and its tappet, of the valvefor regulating pressure in the controlling pipes, and meanssubstantially as described whereby said valve is intermittently andautomatically connected to and disconnected from the lever during thethrow of the latter, substantially as and for the purposes hereinbeforeset forth.

4. In combination, the operating lever and its slotted tappet, the twoindicator pins, and pneumatic appliances for operating said pinsconnected to and controlled in their action by the movement of theswitch, whereby one or the other of the pins is caused to engage andlock the tappet before the lever completes its full throw in eitherdirection until after the switch has been fully shifted, substantiallyas hereinbefore set forth.

5. The indicator pins, and the reciprocatory pistons therein to whichsaid pins are severally connected, in combination with the switch, theslide valve mechanism connected to and operated by the switch, andcontrolling two sets of ports one for each indicator cylinder andconnections whereby when one indicator cylinder is opened to its airexhaust or reducing port, the other is opened to its air supply orpressure port, and vice versa.

6. The combination of the reciprocatory rod 5, the valve shiftingknockers thereon, the valve mechanism actuated by said knockers at ornear the conclusion of the movement of the rodin either direction,theindicator cylinders and mechanism, and connections between the sameand the valve mechanism, substantially as and for the purposeshereinbefore set forth.

'7. In combination with the valve chest or case and the controllingpipes, the two pneumatic pistons provided with notched stems and thetransversely sliding dog arranged between said stems and operating tolock and release each stem alternately at the times and in the mannersubstantially as hereinbefore set forth... 7

8. The equalizing piston, its chest and controlling pipe, in combinationwith the valve operated by said piston, and the ports controlled by saidvalve, the supply port having direct communication with a source ofcompressed air supply and being closed at all times by the valve fromcommunication with the compressed air received in the chest throughthecontrolling pipe.

9. The equalizing piston mechanism, in combination with the indicatorcylinder and appliances, substantially as and for the purposeshereinbefore set forth.

In testimony whereof I have hereunto set my hand, before two subscribingwitnesses, this 16th day of February, 1894.

JOHN w. THOMAS, JRQ

Witnesses:

EWELL A. DICK, RoBT. W. COX.

